Abstract
Lake littoral environments are heterogeneous, and different organisms typically show specific responses to this environmental variation. We examined local environmental and spatial factors affecting lake littoral biodiversity and the structuring of assemblages of phytoplankton, zooplankton and macroinvertebrates within and among three basins of a large lake system. We explored congruence of species composition and species richness among the studied organism groups to evaluate their general indicator potential to represent spatial variation in other groups. We expected that effects of water chemistry on plankton assemblages were stronger than effects of habitat characteristics. In contrast, we anticipated stronger effects of habitat on macroinvertebrates due to their mainly benthic mode of life. We also expected that within-basin spatial effects would be strongest on macroinvertebrates and weakest on phytoplankton. We predicted weak congruence in assemblage composition and species richness among the organism groups. Phytoplankton assemblages were mainly structured by the shared effects of water chemistry and large-scale spatial factors. In contrast to our expectations, habitat effects were stronger than water chemistry effects on zooplankton assemblages. However, as expected, macroinvertebrate species composition and richness were mainly affected by habitat conditions. Among-group congruence was weak for assemblage composition and insignificant for richness. Albeit weak, congruence was strongest between phytoplankton and zooplankton assemblages, as we expected. In summary, our analyses do not support the idea of using a single organism group as a wholesale biodiversity indicator.
Highlights
Freshwater biodiversity is currently jeopardized by various anthropogenic effects (Reid et al 2019), which necessitates the use of robust and efficient biodiversity indicators (Heino 2015)
Phytoplankton community composition was characteristic to the basins of the lake system, as 40% of the total variation was related to basin and unique proportion explained by the basin alone was 10%
Conductivity and pH were the water chemistry variables significantly associated with phytoplankton composition
Summary
Freshwater biodiversity is currently jeopardized by various anthropogenic effects (Reid et al 2019), which necessitates the use of robust and efficient biodiversity indicators (Heino 2015). Habitat characteristics including shoreline morphometry are the most important factors affecting biological communities in large lakes with extensive wind fetch but relatively limited water quality gradients (Tolonen et al 2001, 2005; Tolonen and Hamalainen 2010). In addition to local environmental conditions, spatial factors associated with organisms’ dispersal rates or physical barriers (Mouquet and Loreau 2003; Heino et al 2015) may be important in influencing littoral communities at both among-lake (Johnson and Goedkoop 2002; Heino and Tolonen 2017) and within-lake (Vilmi et al 2016; Tolonen et al 2017) spatial scales. Spatial structuring of biological communities may be related to mass effects, i.e. dispersal of abundant species from large source habitat patches to suboptimal conditions in smaller sink patches (Mouquet and Loreau 2003). Dispersal limitation with low rates of dispersal and physical barriers to dispersal are more likely to create spatial community patterns at large spatial scales (Heino et al 2015)
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